Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque 
h,w=map(int,input().split())
s=[list(input()) for i in range(h)]
ans=0
for i in range(h):
    for j in range(w):
        if s[i][j]==".":
            ans+=1
q=deque([[0,0]])
dx=[1,0,-1,0]
dy=[0,1,0,-1]
s[0][0]=0
while q:
    p=q.popleft()
    if p[0]==h-1 and p[1]==w-1:
        break
    for i in range(4):
        x=p[0]+dx[i]
        y=p[1]+dy[i]
        if 0<=x<h and 0<=y<w and s[x][y]==".":
            s[x][y]=s[p[0]][p[1]]+1
            q.append([x,y])
print(-1 if s[-1][-1]=="." else ans-s[-1][-1]-1)